Glossary
Time Travel
Movement through the Fourth Dimension. In Sparrow's book it is possible only inside a Tangent Universe, and only for the Manipulated Dead and, at the end, the Artifact.
The film supports both a physics reading (Monnitoff's wormholes, Hawking's A Brief History of Time) and Sparrow's metaphysical one. Frank travels in time as a Manipulated Dead; the jet engine travels back 28 days; Donnie, in some readings, travels back to his bed on October 2. Whether the loop is "real" or a dying vision is the question every ending-explained article is really about.
Defined in The Philosophy of Time Travel